Comparing VDI, VHD, and VMDK Formats: Which is Superior and How to Convert Among Them?

Virtual machines store their data in image file formats. The image file format a virtual machine uses depends on the platform you’re deploying the machine. If you’re running Oracle’s VirtualBox VM, the files would be saved in VDI (VirtualBox Disk Image) format; similarly, if you’re deploying a local Microsoft Hyper-V VM (Virtual Desktop), the data would be saved in VHD (Virtual Hard Disk) format, and if you use VMware products for hosting VMs, the data would be saved as VMDK (Virtual Machine Disk) in a VMFS partition.

It is important to learn about these three common virtual disk formats and how to handle them – especially if you’re an IT admin who handles multiple virtual machines across platforms. This article provides clear definitions and handy information regarding these virtual disk formats.

What is VHD (Virtual Hard Disk)?

VHD (Virtual Hard Disk) is Microsoft’s virtual hard disk format for its Hyper-V and Virtual Server platforms. The file format, originally developed by Connectix, is one of the three most popular virtual hard drive formats. Microsoft has since replaced it with VHDX (Virtual Hard Disk v2), which offers a larger storage capacity of up to 64 TB. But now? The Microsoft platforms that utilize these virtual disk formats are now defunct.

Regardless, the VHD format is still widely supported by other virtualization platforms – actually, it’s the newer version, VHDX, since it offers more storage capacity (64TB) than VHD (2TB). VHD/VHDX files stay on the host OS, there are quite a few sub-types of this Microsoft virtual hard drive format:

• Fixed Hard Disk Image: Raw disk image file, typically the same size as the virtual disk and includes a VHD footer.
• Expandable (or Dynamic) Disk Image: Includes a header and footer, and is usually a large file - as large as the data it stores.
• Differencing Hard Disk Image: This VHD image type saves all changes on the main VHD file to a child image, with an “undo” option so you can revert the changes.
• Pass-Through Disk Image: This VHD image type links with the physical hard drive on the host or one of its partitions.

Features of VHD:

• Resides on the host OS
• Supports multiple image types
• Allows differencing and snapshotting
• Using PowerShell scripts, you can convert VHD to VHDX.

Pros:

• You can modify VM configurations from the host server
• Ability to run multiple OSes on one hard drive without creating additional partitions
• It is possible to undo and redo changes to a VHD file
• You can create preset configurations

Cons:

• A corrupted VHD or VHDX file can crash your Windows OS
• VHD has a storage limit of just 2TB
• Its native platforms are currently obsolete.
• VHDX is very limited to Hyper-V

VHD Files Recovery:

VHD files can be recovered from a backup (if you made one earlier) or using a VHD file recovery tool. There are actually a good number of VHD recovery programs, including enterprise-level software solutions.

Converting Between VDI, VHD, and VMDK Formats

It’s actually possible to convert from one virtual disk format to another. However, in most cases, the conversion comes out “failed.” So it is best to use each virtual disk format with its supported applications. If you still want to know how to convert between these formats, hereunder are the procedures.

Converting Between VDI and VHD Formats

Convert VDI to VHD

To convert a VDI (VirtualBox Disk Image) file to a VHD (Virtual Hard Disk) file used by platforms like Microsoft Hyper-V and Azure, you can use several tools, including command-line utilities. Here’s how to do it using VBoxManage, which is a part of the VirtualBox installation, and using qemu-img for Linux users.

Method 1: Using VBoxManage

VBoxManage is the command-line utility included with VirtualBox that allows for various operations on VirtualBox virtual machines and disks. Here’s how you can convert a VDI file to a VHD:

1. 1. Open your command prompt or terminal.

2. 2. Run the following command:

   bash Copy code

   VBoxManage clonehd "source.vdi" "destination.vhd" --format VHD

   Replace source.vdi with the path to your original VDI file and destination.vhd with the path where you want the VHD file to be saved.

Method 2: Using qemu-img (Linux)

For Linux users, qemu-img is a versatile tool that can handle disk image conversion between different formats. Here’s how to use it to convert a VDI to a VHD:

1. 1. Install qemu (if it’s not already installed):

   • Ubuntu/Debian:
     bash Copy code

     sudo apt-get install qemu-utils
   • CentOS/RHEL:
     bash Copy code

     sudo yum install qemu-img

2. 2. Convert the file using the following command:

   bash Copy code

   qemu-img convert -f vdi -O vpc source.vdi destination.vhd

   In this command, replace source.vdi with the path to your VDI file and destination.vhd with the desired output file path. The format vpc refers to the VHD format used by Virtual PC and is compatible with Microsoft Hyper-V.

Converting Between VDI and VMDK Formats

Convert VDI to VMDK/h4>

Converting a VDI (VirtualBox Disk Image) file to a VMDK (VMware Disk) file involves a few steps, and you can achieve this using a variety of tools, including command-line utilities and graphical software. Here are the common methods:

Method 1: Using VBoxManage

VBoxManage is a command-line utility that comes with VirtualBox. It can be used to convert a VDI file to a VMDK file. Here's how you can do it:

1. 1. Open your command prompt or terminal.

2. 2. Use the following command to convert the VDI file to VMDK:

   bash Copy code

   VBoxManage clonehd --format VMDK input.vdi output.vmdk

   Replace input.vdi with the path to your VDI file and output.vmdk with the desired path for the VMDK file.

Method 2: Using VMware Converter

VMware Converter is a software offered by VMware that can convert entire machines, virtual machine formats, or disk files. It’s particularly useful for more complex setups or system migrations. Here’s a brief guide:

1. 1. Download and install VMware Converter from the VMware website.
2. 2. Launch VMware Converter and choose to convert a machine or a system image.
3. 3. Select the source type as Virtual Appliances and browse to your VDI file.
4. 4. Follow the prompts to set up the conversion specifics and choose VMDK as the target format.

Method 3: Using qemu-img (for Linux users)

If you're on a Linux system, you can use the qemu-img tool to convert between various file formats, including VDI to VMDK. Here’s how:

1. 1. Install qemu (if it’s not installed):

   • For Ubuntu/Debian:
     bash Copy code

     sudo apt-get install qemu-utils
   • For CentOS/RHEL:
     bash Copy code

     sudo yum install qemu-img

2. 2. Convert the file using the following command:

   bash Copy code

   qemu-img convert -f vdi -O vmdk input.vdi output.vmdk

   Again, replace input.vdi with the path to your VDI file and output.vmdk with the desired path for the VMDK file.

Converting between VHD and VMDK Formats

Convert VHD to VMDK

To convert a VHD (Virtual Hard Disk) file to a VMDK (VMware Disk) file, you can use several available tools and methods. Here, I'll guide you through using VBoxManage, which is part of VirtualBox, and qemu-img, commonly used in Linux environments.

Method 1: Using VBoxManage

VBoxManage is a versatile command-line utility included with VirtualBox that allows you to manage VirtualBox-related operations. It can also handle disk conversion tasks. Here’s how to convert a VHD file to VMDK:

1. 1. Open a command prompt or terminal window.

2. 2. Use the following command:

   bash Copy code

   VBoxManage clonehd "source.vhd" "destination.vmdk" --format VMDK

   Replace source.vhd with the path to your VHD file and destination.vmdk with the path where you want the VMDK file to be saved.

Method 2: Using qemu-img (Linux)

For those using a Linux system, qemu-img is an effective tool for converting disk images between different formats. To convert a VHD file to a VMDK:

1. 1. Install qemu-img if not already installed:

   • Ubuntu/Debian:
     bash Copy code

     sudo apt-get install qemu-utils
   • CentOS/RHEL:
     bash Copy code

     sudo yum install qemu-img

2. 2. Convert the file using the following command:

   bash Copy code

   qemu-img convert -f vpc -O vmdk source.vhd destination.vmdk

   In this command, replace source.vhd with the path to your VHD file and destination.vmdk with the path where you want the VMDK file to be created. The -f vpc flag specifies the format of the source image (in this case, Virtual PC compatible, which covers VHD files).

Conclusion

VHD, VDI, and VMDK are the three most used virtual disk formats and are supported by virtualization platforms. These image formats can be tweaked and converted to different formats, but the conversion doesn’t always come out good.

VMDK is currently the most preferred virtual hard disk format, thanks to VMware’s wide offerings and impressive modern tech infusion across its hypervisors and virtualization platforms. If you lose any of the virtual hard drive files, the DiskInternals VMFS Recovery can help you get them back.